1 files changed, 67 insertions, 0 deletions
diff --git a/source/blender/compositor/realtime_compositor/intern/reduce_to_single_value_operation.cc b/source/blender/compositor/realtime_compositor/intern/reduce_to_single_value_operation.cc
new file mode 100644
index 00000000000..acc9b4ab7d6
--- /dev/null
+++ b/source/blender/compositor/realtime_compositor/intern/reduce_to_single_value_operation.cc
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "GPU_state.h"
+#include "GPU_texture.h"
+
+#include "MEM_guardedalloc.h"
+
+#include "COM_context.hh"
+#include "COM_input_descriptor.hh"
+#include "COM_reduce_to_single_value_operation.hh"
+#include "COM_result.hh"
+
+namespace blender::realtime_compositor {
+
+ReduceToSingleValueOperation::ReduceToSingleValueOperation(Context &context, ResultType type)
+    : SimpleOperation(context)
+{
+  InputDescriptor input_descriptor;
+  input_descriptor.type = type;
+  declare_input_descriptor(input_descriptor);
+  populate_result(Result(type, texture_pool()));
+}
+
+void ReduceToSingleValueOperation::execute()
+{
+  /* Make sure any prior writes to the texture are reflected before downloading it. */
+  GPU_memory_barrier(GPU_BARRIER_TEXTURE_UPDATE);
+
+  const Result &input = get_input();
+  float *pixel = static_cast<float *>(GPU_texture_read(input.texture(), GPU_DATA_FLOAT, 0));
+
+  Result &result = get_result();
+  result.allocate_single_value();
+  switch (result.type()) {
+    case ResultType::Color:
+      result.set_color_value(pixel);
+      break;
+    case ResultType::Vector:
+      result.set_vector_value(pixel);
+      break;
+    case ResultType::Float:
+      result.set_float_value(*pixel);
+      break;
+  }
+
+  MEM_freeN(pixel);
+}
+
+SimpleOperation *ReduceToSingleValueOperation::construct_if_needed(Context &context,
+                                                                   const Result &input_result)
+{
+  /* Input result is already a single value, the operation is not needed. */
+  if (input_result.is_single_value()) {
+    return nullptr;
+  }
+
+  /* The input is a full sized texture and can't be reduced to a single value, the operation is not
+   * needed. */
+  if (input_result.domain().size != int2(1)) {
+    return nullptr;
+  }
+
+  /* The input is a texture of a single pixel and can be reduced to a single value. */
+  return new ReduceToSingleValueOperation(context, input_result.type());
+}
+
+}  // namespace blender::realtime_compositor